The graph below shows the LD50 for two different species of mice after being exposed to a mutagen for 30 days.
Based on the data in the graph, which of the following should be used to calculate the difference in LD50 for the two different species of mice?
A (200mg−100mg) / 2
B (490mg/50) − (575mg/50)
C 575mg − 490mg
D (600mg×50) / 30 days